1. Field of the Invention
The present invention relates to a lubricating oil supply apparatus for supplying lubricating oil to lubricating portions such as gear meshing portions, bearing portions, sliding portions, friction surfaces of hydraulic engaging elements, or the like of a hydraulically operated vehicular transmission.
2. Description of Related Art
As this kind of apparatus, there has hitherto been known one in which, as can be seen in Japanese Published Unexamined Patent Application No. 69362/1985, oil to be discharged from an oil discharge port of a pressure control value such as a regulator valve or the like which is provided in a hydraulic control circuit of a transmission, is supplied to lubricating portions of the transmission via a lubricating oil passage which is communicated with the oil discharge port.
In the above-described conventional apparatus, it is so arranged that a constant amount of lubricating oil is supplied to the lubricating portions regardless of the temperature of the transmission. Therefore, an unnecessarily large amount of lubricating oil is supplied when the viscosity thereof is high at a low temperature of the transmission. As a result, a friction increases and, consequently, the running performance decreases, or the specific fuel consumption becomes poor. Further, if lubricating oil of high viscosity is supplied to friction surfaces of hydraulic engaging elements, there will occur a dragging between the friction surfaces, with the result that there is a possibility of lowering the durability of the hydraulic engaging elements.
By the way, the change in the required amount of lubricating oil due to the temperature of the transmission varies in each lubricating portion. For example, a relatively large amount of lubricating oil is required to be supplied to the lubricating portions of high-speed transmission train side even at a low temperature of the transmission, but the amount of lubricating oil to be supplied to the lubricating portions of low-speed transmission train side may be small.